1. Field of the Invention
The present invention relates to a device for driving a motor of a disk device provided in, for example, an electronic still video camera, and more particularly, to a drive signal generating device which generates a pulse signal for driving the motor.
2. Description of the Related Art
In an electronic still camera, or a built-in type VTR camera, a magnetic disk or a magnetic tape is used as a recording medium, and a motor for driving the magnetic disk or the magnetic tape is operated by a servo control. In these devices, considering that the dissipation of power is large, and that a battery is used as the power source, in order to keep the dissipation of power as low as possible, a drive circuit for the motor is usually controlled by a PWM (pulse width modulation) method, i.e., a switching regulator method. Electric power for driving the motor is supplied directly to the motor and does not go through a regulator, because if the electric power is supplied through the regulator, the electric power supply efficiency is lowered.
However, in such a conventional construction in which the electric power is supplied directly to the motor, if the source voltage is changed, the servo characteristic for driving the motor is changed. Thus, control of the motor becomes difficult.